Light Limitation Research Articles

Lab‐based multispectral photography for approximating chlorophyll content in Zostera marina

AbstractReduced light is one of the primary threats to seagrass meadows in the coming decades, with reduced light reaching the benthos due to eutrophication. We assessed a multispectral photography technique using near‐infrared photography to estimate chlorophyll content in the seagrass Zostera marina. Using near‐infrared and red wavelength cameras in the lab environment, we measured normalized difference vegetation index (NDVI) in photographs of sampled seagrass leaves. In samples taken from three different environments, we found a positive correlation between lab‐based NDVI and chlorophyll content, with variation attributable to leaf age. In samples grown under different light conditions, we found high levels of NDVI associated with lower light possibly due to seagrass photoacclimation. This method may be used in addition to existing seagrass monitoring methods to collect data on seagrass photic status and estimate chlorophyll content, and detect possible light limitation due to turbidity or high epibiota cover. The relatively low cost and time required for this method may make it useful where researchers are already collecting and imaging seagrass as part of routine monitoring.

Light-responsive smart nanocarriers for wirelessly controlled photodynamic therapy for prostate cancers.

Photodynamic therapy (PDT) is an effective non-invasive or minimally invasive treatment method against different tumors. Loading photosensitizers in nanocarriers can potentially increase their accumulation in tumor sites. However, the PDT efficacy may be hindered because of self-quenching of the encapsulated photosensitizer and the small diffusion radii of the generated reactive oxygen species (ROS). Herein, light responsive nano assemblies composed of (Polyethylene glycol)-block-poly(4,5-dimethoxy-2-nitrobenzylmethacrylate) (PEG-b-PNBMA) were designed and loaded with the photosensitizer, Rose Bengal lactone (RB), to act as a smart nanocarrier (RB-M) for the delivery of the photosensitizer. A wirelessly activated light-emitting diode (LED) implant was designed to programmatically induce the release of the loaded RB and activate PDT after diffusion of RB into the cytoplasm. The results showed that sequential '405-580 nm' irradiation of the RB-M treated 22RV1 cells resulted in the highest PDT outcome among different irradiation protocols. The combination of this smart nanocarrier and sequential '405-580 nm' irradiation strategy exhibited good PDT efficacy against 2D 22RV1 prostate cancer cells as well as 3D cancer cell spheroids. This platform overcome the light penetration limitations in PDT, and can potentially be applied in cancer bearing patients who are unfit for chemotherapy. STATEMENT OF SIGNIFICANCE: Nanocarriers for the delivery of photosensitizer in photodynamic therapy may result in relatively low therapeutic efficacy because of self-quenching of the encapsulated photosensitizer and the small diffusion radii of the generated reactive oxygen species (ROS). Light responsive smart nanocarriers can potentially overcome this challenge. In this study, a light responsive polymer (Polyethylene glycol)-block-poly(4,5-dimethoxy-2-nitrobenzylmethacrylate) (PEG-b-PNBMA) was synthesized and utilized to fabricate the smart nanocarrier. A wirelessly activated light-emitting diode (LED) implant was designed for light delivery in deep tissue. This new approach permits wirelessly and programmatically control of photosensitizer release and PDT activation under deep tissue, thus significantly enhancing PDT efficacy against prostate cancer cells as well as 3D cancer cell spheroids. This design should have a significant impact on controllable PDT under deep tissue.

Role of feeding and physiological trade-offs in sustaining resilience of the coral Galaxea fascicularis to light limitation

Role of feeding and physiological trade-offs in sustaining resilience of the coral Galaxea fascicularis to light limitation

Potential Predictability of the Spring Bloom in the Southern Ocean Sea Ice Zone

AbstractEvery austral spring when Antarctic sea ice melts, favorable growing conditions lead to an intense phytoplankton bloom, which supports much of the local marine ecosystem. Recent studies have found that Antarctic sea ice is predictable several years in advance, suggesting that the spring bloom might exhibit similar predictability. Using a suite of perfect model predictability experiments, we find that November net primary production (NPP) is potentially predictable 7 to 10 years in advance in many Southern Ocean regions. Sea ice extent predictability peaks in late winter, followed by absorbed shortwave radiation and NPP with a 2 to 3 months lag. This seasonal progression of predictability supports our hypothesis that sea ice and light limitation control the inherent predictability of the spring bloom. Our results suggest skillful interannual predictions of NPP may be achievable, with implications for managing fisheries and the marine ecosystem, and guiding conservation policy in the Southern Ocean.

Super-Resolution Microscopy of the Bacterial Cell Wall Labeled by Fluorescent D-Amino Acids.

Fluorescent D-amino acids (FDAAs) enable in situ visualization of bacterial cell wall synthesis via their incorporation into peptidoglycan (PG) crosslinks. When combined with super-resolution microscopy, FDAAs allow the details of cell wall synthesis to be resolved beyond the diffraction limit of visible light. Here, we describe using the super-resolution method of single-molecule localization microscopy (SMLM) in conjunction with two newly synthesized FDAAs (sCy5DA and sCy5DL_amide) to resolve bacterial PG at the nanoscale in a variety of species, including Gram-negative, Gram-positive, and mycobacteria.

Proportion of dead cells in phytoplankton modulates community structure

The growth and death of phytoplankton are two key processes that affect structure and function of marine ecosystem. However, current understanding is elaborated from the perspective of growth, and relatively little is known about the environment-driven death of phytoplankton. Our study is aimed to elucidate the differences in group-specific proportion of dead cells and their effects on community structure. Based on flow cytometry analysis, the proportion of dead cells among eukaryotic phytoplankton groups was analyzed in the oligotrophic South China Sea. The eukaryotic phytoplankton were divided into five groups (eukaryotic group 1, eukaryotic group 2, eukaryotic group 3, cryptophytes, and eukaryotic group 4) with successively larger cell size from pico to micro. The larger cells (from nano to micro size) had a higher proportion of dead cells and a lower relative abundance. Only the group of large cells showed a complete correspondence between the proportion of dead cells and abundance in the vertical profile. Above the deep chlorophyll maximum layer, death induced by nutrient limitation was apparent in most groups, and the larger the cell size, the greater the limitation. Below the deep chlorophyll maximum layer, all groups were light-limited, but differences in the degree of light limitation among groups were not significant. These results suggested that differences in cell size contribute to some extent to differences in the proportion of dead cells among groups, making the proportion of dead cells important in regulating community structure and thus further influencing the structure and function of pelagic marine ecosystems.

Dominance of photo over chromatic acclimation strategies by habitat-forming mesophotic red algae.

Red coralline algae are the deepest living macroalgae, capable of creating spatially complex reefs from the intertidal to 100+ m depth with global ecological and biogeochemical significance. How these algae maintain photosynthetic function under increasingly limiting light intensity and spectral availability is key to explaining their large depth distribution. Here, we investigated the photo- and chromatic acclimation and morphological change of free-living red coralline algae towards mesophotic depths in the Fernando do Noronha archipelago, Brazil. From 13 to 86 m depth, thalli tended to become smaller and less complex. We observed a dominance of the photo-acclimatory response, characterized by an increase in photosynthetic efficiency and a decrease in maximum electron transport rate. Chromatic acclimation was generally stable across the euphotic-mesophotic transition with no clear depth trend. Taxonomic comparisons suggest these photosynthetic strategies are conserved to at least the Order level. Light saturation necessitated the use of photoprotection to 65 m depth, while optimal light levels were met at 86 m. Changes to the light environment (e.g. reduced water clarity) due to human activities therefore places these mesophotic algae at risk of light limitation, necessitating the importance of maintaining good water quality for the conservation and protection of mesophotic habitats.

High potential but low achievement: Frequent disturbance constrains the light use efficiency of river ecosystems

AbstractWe rarely consider light limitation in ecosystem productivity, yet light limitation is a major constraint on river autotrophy. Because the light that reaches benthic autotrophs must first pass through terrestrial vegetation and an overlying water column that can be loaded with sediments or colored organic material, there is strong selection for river autotrophs to have high light use efficiencies (LUEs), that is, the efficiency at which light energy is converted to biomass. In contrast to prior studies that have estimated river LUE on single days, we calculated continuous LUE over more than 6 full years for 64 free‐flowing rivers across the United States. This dataset represents the largest compilation of continuous estimates of daily rates of gross primary productivity (GPP) and daily light inputs from which we calculated daily estimates of LUE. Early estimates of LUE in rivers found that clearwater springs with stable flows could achieve LUEs of 4%, much higher than LUEs reported for terrestrial plants. We found that 53% of the rivers in our dataset have LUEs that exceed 4% on at least one day of their time series. Because of the high variability in daily LUE, measurements taken on any given day may misrepresent a river ecosystem's annual LUE. Though most rivers share a high potential, the mean annual LUE of all rivers in our dataset is much lower, only 0.5%. We found that rivers with more variable flow regimes had lower annual LUEs, which indicates that LUE is constrained by hydrologic disturbances that remove, bury, or shade autotrophic biomass. Comparisons of LUE across ecosystems allow us to reframe our view of rivers, by recognizing the high efficiency with which they convert light to biomass compared with lentic, marine, and terrestrial ecosystems.

Responses of Phytoplankton Communities to Internal Waves in Oligotrophic Oceans

AbstractUnderstanding the potential impacts of internal waves on phytoplankton communities in oligotrophic oceans remains an important research challenge. In this study, we elucidated the impact of internal waves on phytoplankton communities through a comprehensive 154‐hr time‐series of observations in the South China Sea (SCS). We identified distinctive variations in phytoplankton pigment biomass and composition across the upper, middle, and lower layers of the euphotic zone, which we attributed to the perturbations triggered by internal waves. Phytoplankton other than Prochlorococcus in the lower, nutrient‐replete layer likely benefitted from allochthonous nutrients introduced by internal waves, but their growth rates were constrained by light limitation, and their pigment biomass was held in check by microzooplankton grazing. In contrast, in the upper, nutrient‐depleted layer, the relative abundance of Prochlorococcus increased, likely because of the ammonium regenerated by zooplankton. The middle layer, characterized as the deep chlorophyll maximum layer, exhibited a dynamic equilibrium characterized by nutrient and light co‐limitation. This equilibrium resulted in high nitrate assimilation and growth by phytoplankton. The balancing of those rates by significant grazing losses maintained total chlorophyll a concentrations at a high level. Based on these findings, we proposed a three‐layer euphotic zone structure characterized by distinct physiological conditions, nutrient‐light dynamics, grazing pressure, and phytoplankton responses to internal waves. This three‐layer paradigm elucidated the intricate interplay between internal waves and phytoplankton communities and provided insights into the mechanisms that govern primary production and carbon cycling in oligotrophic oceanic ecosystems.

Livestock grazing promotes legume abundance under increased nutrient loads: Mechanistic evidence from a temperate grassland

AbstractQuestionLegumes are a key component of rangelands because they play an important role in animal nutrition and the entrance of nitrogen (N) into ecosystems through symbiotic fixation. Legume abundance is commonly low in N‐enriched environments because of competition with grasses and non‐legume forbs. Both haying and livestock grazing remove plant biomass and reduce light limitation to plant growth, with the difference that livestock may selectively consume legumes. This study examines how legumes respond to grazing, haying and fertilization, and what mechanisms explain legume abundance in rangelands.LocationFlooding Pampa, Argentina.MethodsWe performed two manipulation field experiments over 3 years. First, a factorial of rangeland management (intact, haying, or grazing) under two nutrient levels (ambient and increased N, phosphorus [P] and potassium [K]); and second, a factorial of rangeland management (intact or haying) and N × P addition. We evaluated legume, grass and non‐legume forb abundance and ground‐level light in three to five replicates of our experiments over 3 years.ResultsNPK fertilization increased legume abundance consistently under grazing, and temporarily under haying, but had no effect in the intact grassland. Also, P addition increased legume abundance only under haying when N was not added. Temporal changes in legume abundance were positively associated with changes in ground‐level light, which increased with haying and grazing, but decreased with fertilization in the intact grassland, and negatively with grass abundance.ConclusionsThe negative effects of nutrients on legume abundance were offset by the positive effects of livestock. The reduction in grass competition and increase in ground‐level light due to grazing and haying explained the positive responses of legume abundance to nutrients in this temperate grassland. Our results highlight the importance of considering the interactive response of legume abundance to grazing and fertilization, which are becoming common practices in rangelands.

S-Scheme Heterojunction Photocatalyst for Photocatalytic H2O2 Production: A Review

Hydrogen peroxide (H2O2) is a clean and mild oxidant that is receiving increasing attention. The photocatalytic H2O2 production process utilizes solar energy as an energy source and H2O and O2 as material sources, making it a safe and sustainable process. However, the high recombination rate of photogenerated carriers and the low utilization of visible light limit the photocatalytic production of H2O2. S-scheme heterojunctions can significantly reduce the recombination rate of photogenerated electron–hole pairs and retain a high reduction and oxidation capacity due to the presence of an internal electric field. Therefore, it is necessary to develop S-scheme heterojunction photocatalysts with simple preparation methods and high performance. After a brief introduction of the basic principles and advantages of photocatalytic H2O2 production and S-scheme heterojunctions, this review focuses on the design and application of S-scheme heterojunction photocatalysts in photocatalytic H2O2 production. This paper concludes with a challenge and prospect of the application of S-scheme heterojunction photocatalysts in photocatalytic H2O2 production.

Mountain glaciers influence biogeochemical and ecological characteristics of high‐elevation lakes across the northern Rocky Mountains, USA

AbstractMountain glaciers are retreating rapidly due to climate change, leading to the formation of downstream lakes. However, little is known about the physical and biogeochemical conditions in these lakes across a range of glacial influence. We surveyed alpine lakes fed by both glacial and snowpack meltwaters and those fed by snowpack alone to compare nutrient concentrations, stoichiometry, water clarity, chlorophyll, and zooplankton communities. Total phosphorus (TP) and soluble reactive phosphorus were two times higher in glacial lakes than in non‐glacial lakes, while nitrate concentrations were three times higher. However, organic carbon concentrations in glacial lakes were two times lower than in non‐glacial lakes. The carbon‐to‐phosphorus ratio and the nitrogen‐to‐phosphorus ratio of lake seston increased with water clarity in glacial lakes, suggesting that turbidity from glacial flour increases light limitation and increases stoichiometric food quality for zooplankton in newly formed lakes. However, chlorophyll a concentrations did not differ between lake types. Through structural equation modeling, we found that glaciers exhibit a bidirectional association with nitrate and TP concentrations, perhaps mediated through landscape vegetation and lake clarity. Zooplankton communities in high‐turbidity glacial lakes were largely composed of cyclopoid copepods and rotifers (i.e., non‐filter feeders), while non‐glacial lakes tended to be dominated by calanoid copepods and cladocerans (i.e., filter feeders). Our results show that glacier‐influenced lakes have biogeochemical and ecological characteristics distinct from snow‐fed mountain lakes. Sustained studies are needed to assess the dynamics of these unique features as the influence of the alpine cryosphere fades under ongoing climate change.

Applying community assembly theory to restoration: overcoming dispersal and abiotic filters is key to diversifying California grassland

Ecologists have explored community assembly through the framework of ecological filters, which predicts that species must overcome a series of challenges (i.e. pass through “filters”) to successfully establish in a given community. In the context of restoration, these filters (dispersal, abiotic, and biotic) can be manipulated to alter the resulting plant community by favoring native species or disadvantaging non‐native invasive species. We conducted two studies manipulating assembly filters at two California grassland sites previously dominated by non‐native species. At Site 1, we explored how variations in sequential seeding of native grasses and forbs (to overcome dispersal and biotic filters caused by priority effects) influenced the resulting community. At Site 2, we explored how thatch removal (to overcome the abiotic filter of light limitation) and herbicide‐based weed control (to overcome the biotic filter of competition from non‐native species) influenced the addition of native forbs into a partially restored grassland. Native forbs at Site 1 did not suffer from arriving after grasses, but native grasses benefited when given 1 year priority over forbs. At Site 2, dethatching increased native forb cover in a high rainfall year. Herbicide application reduced non‐native grass cover in dethatched plots without negatively affecting native cover. Native forb and grass cover were significant predictors of non‐native grass cover. However, they accounted for only 29% of the variation observed, suggesting there are other influential factors not considered in this study. Our results suggest that forbs can be incorporated into established native grasslands more successfully after dethatching.

Super-Resolution-Chip: an in-vitro platform that enables super-resolution microscopy of co-cultures and 3D systems.

The development of organs-on-a-chip platforms has revolutionized in-vitro cellular culture by allowing cells to be grown in an environment that better mimics human physiology. However, there is still a challenge in integrating those platforms with advanced imaging technology. This is extremely important when we want to study molecular changes and subcellular processes on the level of a single molecule using super-resolution microscopy (SRM), which has a resolution beyond the diffraction limit of light. Currently, existing platforms that include SRM have certain limitations, either as they only support 2D monocultures, without flow or as they demand a lot of production and handling. In this study, we developed a Super-Res-Chip platform, consisting of a 3D-printed chip and a porous membrane, that could be used to co-culture cells in close proximity either in 2D or in 3D while allowing SRM on both sides of the membrane. To demonstrate the functionality of the device, we co-cultured in endothelial and epithelial cells and used direct stochastic optical reconstruction microscopy (dSTORM) to investigate how glioblastoma cells affect the expression of the gap-junction protein Connexin43 in endothelial cells grown in 2D and in 3D. Cluster analysis of Connexin43 distribution revealed no difference in the number of clusters, their size, or radii, but did identify differences in their density. Furthermore, the spatial resolution was high also when the cells were imaged through the membrane (20-30 nm for x-y) and 10-20 nm when imaged directly both for 2D and 3D conditions. Overall, this chip allows to characterize of complex cellular processes on a molecular scale in an easy manner and improved the capacity for imaging in a single molecule resolution complex cellular organization.

Some Remarks on Hume, Reichenbach, and Einstein’s views on Temporal and Causal Priority in Causation with Objections from Quantum Realm

Stunning new observations and theories deepen the concept of causation. Quantum theory is one of the most striking discovery of contemporary physics, and it challenges many facets of older theories, even though it lies on many assumptions that could not be empirically experimented. In this paper, I will recall the views of Hume, Reichenbach and Einstein about the issue of causation, whereas I will focus on causal priority and temporal priority criteria in causation. Nevertheless, one task that I perform is the interpretation of these ideas by arguing them within the quantum scope. That is, trying to manifest Hume, Reichenbach and Einstein views of causation that I think as close, but I shall avoid putting straight cuts on where they differ. Direction of causal processes is dependent on the direction of time in Hume’s sense while Reichenbach explained the direction of time with irreversible processes, even if he follows the temporal priority criteria of Hume. It is stated that there is nothing faster than light by Einstein, as a result, a cause could not pass the upper limit of light. Crudely put, their thoughts all differ from the principles of quantum, because causation (causation might denote a different meaning in quantum realm) may be able to travel faster than light and the common cause principle between events is rejected in quantum realm.

Why do algal blooms intensify under reduced nitrogen and fluctuating phosphorus conditions: The underappreciated role of non‐algal light attenuation

AbstractLight availability for phytoplankton in shallow lakes is closely related to non‐algal light attenuation (KdNALA, the fractional light absorption by non‐algal substances, such as suspended sediments); thus, significant changes in global wind speed in recent decades may have a profound effect on light availability and algal blooms in shallow lakes. Herein, the eutrophic shallow Lake Taihu was selected to investigate the long‐term dynamics of light availability and its effect on algal blooms. The results showed that KdNALA decreased from approximately 3.5 to 2.5 m−1 with decreasing wind speed from 2005 to 2021, indicating the significantly increased light availability for phytoplankton despite surface photosynthetically active radiation exhibiting limited variability during the study period. In addition, both experimental (i.e., in situ nutrient enrichment experiments) and statistical approaches (i.e., deviations of Trophic State Index subindices) indicated that phytoplankton growth was primarily light‐limited during the study period in Lake Taihu. Consequently, considerable increases in fraction of observed and maximal chlorophyll a yield at given nitrogen or phosphorus concentration were observed and were mostly related to decreasing KdNALA, which implied that decreasing KdNALA allowed phytoplankton utilize “unused nutrient‐capacity” until the additional algal‐turbidity induce further light limitation or nutrient limitation. As the effect of changes in global wind speed on KdNALA and algal growth received limited attention in the existing research, we revealed an underappreciated mechanism by which global changes in wind speed significantly affects algal biomass by influencing light availability, which may have profound effects on future algal bloom mitigation efforts in shallow lakes.

Highly Efficient Photocathodic Protection Performance of ZIS@CNNs Composites under Visible Light

Low isolation efficiency of photogenerated electron-hole pairs and inadequate utilization of visible light limit the application of g-C3N4 nanosheets (CNNs) in photocathodic protection (PCP). Therefore, indium zinc sulfide (ZnIn2S4, ZIS) nanolayers with nano-leaf structures were fabricated on CNNs using a simple hydrothermal method and used as visible light sensitizer and electron donor to improve its PCP performance. Under visible light illumination, the 30% ZIS@CNNs photoelectrode coupled with 316 stainless steel (SS) exhibited the largest photocurrent density of 17.30 μA cm−2 and the highest potential drop of 0.37 V, which was approximately 4 and 7.5 times higher than that of pure CNNs, respectively. The improvement in protection performance may be attributable to the crucial increase in visible light absorption and the terrific enhancement in rapid migration pathways provided using heterogeneous junctions.

Full-spectrum and tunable white light emission of germanate glass-ceramic containing defective Zn2GeO4 and Mn2+ ions

The full-spectrum phosphors are key components for improving the light quality of phosphor-converted white light-emitting diodes (pc-WLEDs). In this work, a novel germanate glass-ceramic (GC) doped with Mn2+ was developed to achieve full-spectrum white light emission deriving from the defective Zn2GeO4 crystalline phase and Mn2+ with multisite occupancy. The defective Zn2GeO4 is crystallized in situ from the well-designed precursor germanate glass by a controllable heat treatment. The energy states of intrinsic defects, including oxygen and zinc vacancies and interstitial zinc and oxygen of Zn2GeO4 in GC, have been studied by first-principles calculations. The luminescence property and the energy transfer mechanism between the defect states and Mn2+ ions in the GC material was proposed. Under the UV excitation, the luminescence property can be tuned by adjusting the distribution of Mn2+ ions in between the glassy and crystalline phases. The correlated color temperature (CCT) and color rendering index (CRI) of the UV-excited full-spectrum white light emission can be tuned over a wide range. This combinatorial strategy of intrinsic defects and multisite ion doping for full-spectrum white light emission in GC, which overcomes the limitation of conventional discontinuous white light emitting materials that emit singly from doping ions, has shown good potential for application in pc-WLEDs.

Fire Characteristics and Hydrologic Connectivity Influence Short‐Term Responses of North Temperate Lakes to Wildfire

AbstractDespite increasing wildfires, few studies have investigated seasonal water quality responses to wildfire characteristics (e.g., burn severity) across a large number of lakes. We monitored 30 total lakes (15 burned, 15 control) monthly following the Greenwood Fire in Minnesota, USA, a lake‐rich region with historically prevalent wildfire. We found increases in median concentrations of total nitrogen (68%), total phosphorus (70%), dissolved organic carbon (127%), total suspended solids (71%), and reduced water clarity (48%) and pH (0.45) in burned lakes. Post‐wildfire responses in drainage lakes were often persistent or cumulative throughout the open‐water season, compared to isolated lakes. Total phosphorus (TP) increased linearly with watershed high‐severity burns, and shoreline high‐severity burns explained more variation in TP than lake morphometry and watershed variables. Post‐wildfire chlorophyll‐a responses were nonsignificant and inconsistent, possibly due to light limitation. Our results suggest that increasing wildfires have significant potential to affect water quality of inland lakes.

Terahertz phononic crystal in plasmonic nanocavity

Interaction between photons and phonons in cavity optomechanical systems provides a new toolbox for quantum information technologies. A GaAs/AlAs pillar multi-optical mode microcavity optomechanical structure can obtain phonons with ultra-high frequency (~THz). However, the optical field cannot be effectively restricted when the diameter of the GaAs/AlAs pillar microcavity decreases below the diffraction limit of light. Here, we design a system that combines Ag nanocavity with GaAs/AlAs phononic superlattices, where phonons with the frequency of 4.2 THz can be confined in a pillar with ~4 nm diameter. The Q c/V reaches 0.22 nm−3, which is ~80 times that of the photonic crystal (PhC) nanobeam and ~100 times that of the hybrid point-defect PhC bowtie plasmonic nanocavity, where Q c is optical quality factor and V is mode volume. The optomechanical single-photon coupling strength can reach 12 MHz, which is an order of magnitude larger than that of the PhC nanobeam. In addition, the mechanical zero-point fluctuation amplitude is 85 fm and the efficient mass is 0.27 zg, which is much smaller than the PhC nanobeam. The phononic superlattice-Ag nanocavity optomechanical devices hold great potential for applications in the field of integrated quantum optomechanics, quantum information, and terahertz-light transducer.